Aggregator

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0143 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to be low on Thursday. Hurricane Helene will be absorbed into the upper-level flow across the eastern US with widespread rainfall anticipated. Across the central and western US, a ridge of high pressure will remain in place with generally light winds. As such, no overlap of critically dry fuels with Elevated/Critical conditions is expected. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0143 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to be low on Thursday. Hurricane Helene will be absorbed into the upper-level flow across the eastern US with widespread rainfall anticipated. Across the central and western US, a ridge of high pressure will remain in place with generally light winds. As such, no overlap of critically dry fuels with Elevated/Critical conditions is expected. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0143 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to be low on Thursday. Hurricane Helene will be absorbed into the upper-level flow across the eastern US with widespread rainfall anticipated. Across the central and western US, a ridge of high pressure will remain in place with generally light winds. As such, no overlap of critically dry fuels with Elevated/Critical conditions is expected. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0113 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A trough will traverse the northern portion of the western US ridge today, bringing enhanced mid-level flow over the Cascades into western Washington and Oregon. Across southwestern Oregon, sustained winds around 15-20 mph will overlap relative humidity reductions to around 20-25 percent. Elevated fire weather conditions will be possible. Receptive fuels in this region are spotty, which leads to low confidence in including an area at this time. In the lee of the Bighorn Mountains in Wyoming, some Elevated to Critical fire weather conditions will be possible. Overall, sustained Elevated to Critical wind speeds appear brief and localized. ..Thornton.. 09/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST GEORGIA INTO THE SOUTHERN SC COASTAL VICINITY... ...SUMMARY... Tropical Cyclone Helene is forecast to move inland across northern Florida and Georgia on Thursday. A risk for tropical-cyclone tornadoes will accompany this system, particularly from the central Florida Peninsula into southeast Georgia and parts of the Midlands and Low Country of South Carolina. ...FL/GA/SC/southeast NC... Latest forecast track guidance from the National Hurricane Center has Helene making landfall in the vicinity of the Florida Big Bend Thursday evening. As the storm tracks northward across the eastern Gulf of Mexico, low and mid level flow fields will increase from central FL into southeast GA and coastal SC during the day. Forecast soundings from most forecast guidance show very large, favorably curved low-level hodographs for rotating supercells within convective bands well east/northeast of the center of Helene. Surface dewpoints are forecast to increase into the mid 70s F, resulting in greater than 125 J/kg 0-3 km MLCAPE from north FL into southeast GA and southern coastal SC. Furthermore, looking at historical tropical cyclone tornado data, adjusting for the expected track/storm motion of Helene and even distance from the center, previous cyclone analogs have produced several tornadoes within the favored northeast quadrant. Given a consistent, favorable signal across ensemble, deterministic, CAMs and calibrated guidance, an Enhanced risk (level 3 of 5) has been included, driven by a 10 percent tornado probability, across southeast GA into southern coastal SC. ..Leitman.. 09/25/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE GULF COAST INTO THE SOUTHERN/CENTRAL APPALACHIANS AND FLORIDA PENINSULA... ...SUMMARY... Isolated severe storms are possible later today from parts of the Southeast and central/southern Appalachians to the Texas/Louisiana Gulf Coast. Some tornado threat may develop across the Florida Peninsula by this evening, in association with Tropical Cyclone Helene. ...Synopsis... The upper-level pattern across much of the CONUS will become rather complex today and tonight. Tropical Cyclone Helene is forecast to intensify as a hurricane as it begins to move north-northeastward across the eastern Gulf of Mexico; see NHC forecasts and advisories for more information. A mid/upper-level low that will initially be over the mid MS Valley is expected to slow down and eventually move southward, as it begins to interact with Helene. A northern-stream mid/upper-level trough is expected to amplify as it moves east-southeastward toward the lower Great Lakes region. A seasonably strong mid/upper-level shortwave trough will move across the Northwest through the day and into the evening. ...Parts of the TX Gulf Coast into the Southeast and southern Appalachians... Widespread precipitation is expected from parts of the Southeast into the southern Appalachians, due to the combined influence of the mid/upper-level flow to the west and moisture streaming north from the Gulf of Mexico and Helene. While this will tend to limit available buoyancy with time, a few strong storms will be possible with initial development, with preconvective MLCAPE of around 1000 J/kg and generally favorable deep-layer shear. Locally damaging gusts and perhaps a tornado could accompany the strongest storms, before low/midlevel lapse rates and buoyancy become increasingly weak with time, and an outflow-reinforced front sags southward across the region. Compared to areas farther east, somewhat stronger diurnal destabilization will be possible from parts of central/east TX into LA, and perhaps into MS, with MLCAPE potentially increasing above 1500 J/kg. Isolated to widely scattered storm development will be possible near a southward-moving cold front. Effective shear will generally range from 25-35 kt, and a few modestly organized storms are possible. Isolated damaging gusts could accompany the strongest storms within this regime. ...Florida Peninsula and Keys... Helene's wind field is forecast to be rather large, especially on the east side of the circulation. This will result in strengthening low-level shear/SRH across the Florida Peninsula during the day and especially into the evening/overnight. Instability will likely remain rather weak, and details regarding the intensity of any outer rain bands remain uncertain, but some tropical-cyclone tornado threat could evolve across parts of the peninsula and Keys, especially later in the period. ...Upper Ohio Valley into the lower Great Lakes... Weak to locally moderate buoyancy may develop later today from parts of the upper OH Valley into the lower Great Lakes region, between a weakening cold front approaching from the west, and a slow-moving warm front draped from central PA into western NY. Moderate southwesterly midlevel flow will support effective shear of 35-45 kt, sufficient for storm organization. However, with midlevel lapse rates expected to remain rather weak, storm intensity and any attendant severe threat could be relatively limited. Confidence in sufficient destabilization is too low to add probabilities at this time. ...Eastern WA into northern ID and northwest MT... While buoyancy is expected to remain quite weak, relatively steep midlevel lapse rates will support thunderstorm potential from eastern WA into northern ID and northwest MT, in advance of the approaching shortwave trough. Most guidance suggests that instability will remain too weak for an organized severe threat, though rather strong deep-layer flow/shear could support a strong storm or two with locally gusty winds and small hail. Severe probabilities may eventually be needed if confidence increases regarding the development of sufficient instability. ..Dean/Thornton.. 09/25/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE GULF COAST INTO THE SOUTHERN/CENTRAL APPALACHIANS AND FLORIDA PENINSULA... ...SUMMARY... Isolated severe storms are possible later today from parts of the Southeast and central/southern Appalachians to the Texas/Louisiana Gulf Coast. Some tornado threat may develop across the Florida Peninsula by this evening, in association with Tropical Cyclone Helene. ...Synopsis... The upper-level pattern across much of the CONUS will become rather complex today and tonight. Tropical Cyclone Helene is forecast to intensify as a hurricane as it begins to move north-northeastward across the eastern Gulf of Mexico; see NHC forecasts and advisories for more information. A mid/upper-level low that will initially be over the mid MS Valley is expected to slow down and eventually move southward, as it begins to interact with Helene. A northern-stream mid/upper-level trough is expected to amplify as it moves east-southeastward toward the lower Great Lakes region. A seasonably strong mid/upper-level shortwave trough will move across the Northwest through the day and into the evening. ...Parts of the TX Gulf Coast into the Southeast and southern Appalachians... Widespread precipitation is expected from parts of the Southeast into the southern Appalachians, due to the combined influence of the mid/upper-level flow to the west and moisture streaming north from the Gulf of Mexico and Helene. While this will tend to limit available buoyancy with time, a few strong storms will be possible with initial development, with preconvective MLCAPE of around 1000 J/kg and generally favorable deep-layer shear. Locally damaging gusts and perhaps a tornado could accompany the strongest storms, before low/midlevel lapse rates and buoyancy become increasingly weak with time, and an outflow-reinforced front sags southward across the region. Compared to areas farther east, somewhat stronger diurnal destabilization will be possible from parts of central/east TX into LA, and perhaps into MS, with MLCAPE potentially increasing above 1500 J/kg. Isolated to widely scattered storm development will be possible near a southward-moving cold front. Effective shear will generally range from 25-35 kt, and a few modestly organized storms are possible. Isolated damaging gusts could accompany the strongest storms within this regime. ...Florida Peninsula and Keys... Helene's wind field is forecast to be rather large, especially on the east side of the circulation. This will result in strengthening low-level shear/SRH across the Florida Peninsula during the day and especially into the evening/overnight. Instability will likely remain rather weak, and details regarding the intensity of any outer rain bands remain uncertain, but some tropical-cyclone tornado threat could evolve across parts of the peninsula and Keys, especially later in the period. ...Upper Ohio Valley into the lower Great Lakes... Weak to locally moderate buoyancy may develop later today from parts of the upper OH Valley into the lower Great Lakes region, between a weakening cold front approaching from the west, and a slow-moving warm front draped from central PA into western NY. Moderate southwesterly midlevel flow will support effective shear of 35-45 kt, sufficient for storm organization. However, with midlevel lapse rates expected to remain rather weak, storm intensity and any attendant severe threat could be relatively limited. Confidence in sufficient destabilization is too low to add probabilities at this time. ...Eastern WA into northern ID and northwest MT... While buoyancy is expected to remain quite weak, relatively steep midlevel lapse rates will support thunderstorm potential from eastern WA into northern ID and northwest MT, in advance of the approaching shortwave trough. Most guidance suggests that instability will remain too weak for an organized severe threat, though rather strong deep-layer flow/shear could support a strong storm or two with locally gusty winds and small hail. Severe probabilities may eventually be needed if confidence increases regarding the development of sufficient instability. ..Dean/Thornton.. 09/25/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Wed Sep 25 2024 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE GULF COAST INTO THE SOUTHERN/CENTRAL APPALACHIANS AND FLORIDA PENINSULA... ...SUMMARY... Isolated severe storms are possible later today from parts of the Southeast and central/southern Appalachians to the Texas/Louisiana Gulf Coast. Some tornado threat may develop across the Florida Peninsula by this evening, in association with Tropical Cyclone Helene. ...Synopsis... The upper-level pattern across much of the CONUS will become rather complex today and tonight. Tropical Cyclone Helene is forecast to intensify as a hurricane as it begins to move north-northeastward across the eastern Gulf of Mexico; see NHC forecasts and advisories for more information. A mid/upper-level low that will initially be over the mid MS Valley is expected to slow down and eventually move southward, as it begins to interact with Helene. A northern-stream mid/upper-level trough is expected to amplify as it moves east-southeastward toward the lower Great Lakes region. A seasonably strong mid/upper-level shortwave trough will move across the Northwest through the day and into the evening. ...Parts of the TX Gulf Coast into the Southeast and southern Appalachians... Widespread precipitation is expected from parts of the Southeast into the southern Appalachians, due to the combined influence of the mid/upper-level flow to the west and moisture streaming north from the Gulf of Mexico and Helene. While this will tend to limit available buoyancy with time, a few strong storms will be possible with initial development, with preconvective MLCAPE of around 1000 J/kg and generally favorable deep-layer shear. Locally damaging gusts and perhaps a tornado could accompany the strongest storms, before low/midlevel lapse rates and buoyancy become increasingly weak with time, and an outflow-reinforced front sags southward across the region. Compared to areas farther east, somewhat stronger diurnal destabilization will be possible from parts of central/east TX into LA, and perhaps into MS, with MLCAPE potentially increasing above 1500 J/kg. Isolated to widely scattered storm development will be possible near a southward-moving cold front. Effective shear will generally range from 25-35 kt, and a few modestly organized storms are possible. Isolated damaging gusts could accompany the strongest storms within this regime. ...Florida Peninsula and Keys... Helene's wind field is forecast to be rather large, especially on the east side of the circulation. This will result in strengthening low-level shear/SRH across the Florida Peninsula during the day and especially into the evening/overnight. Instability will likely remain rather weak, and details regarding the intensity of any outer rain bands remain uncertain, but some tropical-cyclone tornado threat could evolve across parts of the peninsula and Keys, especially later in the period. ...Upper Ohio Valley into the lower Great Lakes... Weak to locally moderate buoyancy may develop later today from parts of the upper OH Valley into the lower Great Lakes region, between a weakening cold front approaching from the west, and a slow-moving warm front draped from central PA into western NY. Moderate southwesterly midlevel flow will support effective shear of 35-45 kt, sufficient for storm organization. However, with midlevel lapse rates expected to remain rather weak, storm intensity and any attendant severe threat could be relatively limited. Confidence in sufficient destabilization is too low to add probabilities at this time. ...Eastern WA into northern ID and northwest MT... While buoyancy is expected to remain quite weak, relatively steep midlevel lapse rates will support thunderstorm potential from eastern WA into northern ID and northwest MT, in advance of the approaching shortwave trough. Most guidance suggests that instability will remain too weak for an organized severe threat, though rather strong deep-layer flow/shear could support a strong storm or two with locally gusty winds and small hail. Severe probabilities may eventually be needed if confidence increases regarding the development of sufficient instability. ..Dean/Thornton.. 09/25/2024 Read more